Information regarding roadways is usually distributed by direct provision of information to the user, who mainly perceives it visually. For example, more or less visible signs can communicate prohibitions, danger situations or general information.
These signs are often poorly visible, especially in bad weather conditions, and may be a cause of distraction for the user.
Inter-vehicle communication, e.g. over a roadway, is also mainly based on visual signals.
For instance, a user will turn on the appropriate lights for signal positioning and use the special turn indicator lights for direction change.
These systems have the same drawbacks as mentioned above.
However, wireless laser- or radio-based communication systems are currently commercially available.
From US application 2004067787, an antenna is known having a laser emitter, which projects a beam in a predetermined point, the beam being adapted to be captured and decoded by a device that is mounted on driving vehicles.
A drawback of this solution is that it is bulky, unpractical and generally poorly cost-effective, insofar as it requires important investments by the highway company.
U.S. Pat. No. 5,835,203 discloses and claims an inter-vehicle communication system which utilizes a laser beam.
This system has the disadvantage of a difficult fabrication, with a complex and limited data management system.
From U.S. Pat. No. 5,529,138 a laser-based alarm system for motor vehicles is known, wherein a sensor detects the speed of the preceding vehicle and warns or, in another embodiment, automatically brakes the vehicle in danger conditions.
A drawback of this known device is that laser beam data management is complicated, highly elaborate and prone to error.
Other documents, more or less relating to inter-vehicle data communication systems, are US2004093160, U.S. Pat. No. 6,493,123, U.S. Pat. No. 6,014,601, US2003052773, U.S. Pat. No. 3,891,966, FR-A-2694639.
All these documents have the above particular drawbacks, as well as other important limitations.
First, the information is unrelated to external conditions, and remains unchanged regardless of condition variations. For example, in case of traffic congestion or queues, the information is always transmitted from the preceding to the following vehicle, and there is no way to enlarge the transmission range, which might be of vital importance.